Turbo lag? - Page 2 - Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community

Ryephile · 11-07-2012, 05:37 PM

Boost Threshold = The power in which a certain level of boost is achieved. This is usually best understood as the RPM in which the turbo "kicks in"

Turbo Lag = The time needed within the operational envelope of the turbo [between the compressors' choke and surge lines] for the turbo to create noteworthy airflow beyond natural aspiration versus the throttle opening.

For what it's worth, attempting to describe turbo lag below the boost threshold is a misapplication of terminology.

Example: A GT35R is bolted onto your friends Evo IX. It has a dyno-pull WOT boost threshold of 5k RPM [just go with it]. If he floors it at 3k RPM, the car is turtle slow and essentially naturally aspirated. This is not turbo lag, and the turbo is operating below it's boost threshold. He keeps his foot to the floor, and once the engine reaches 5k RPM, the turbo reaches boost and the car rockets away into the sunset. Now let's say he's downshifted and is cruising along steady at 6k RPM, then floors the throttle. The turbo takes time to spool, this is the turbo lag. The engine as a system also has to create a certain amount of power to spool the turbo. Once that certain level happens, the car rockets off into the horizon. You've now hit the boost threshold, even though it happened at 6k.

If my example is confusing, it's also nicely explained on Wikipedia.

gmookher · 01-15-2013, 06:06 PM

go test drive some cars, you aint gonna get it sittin there...

wbradley · 01-15-2013, 07:42 PM

When you hear the turbo spooling but the car still moves like its NA, thats the lag. Once you feel the punch the lag is gone.

TheRipler · 01-15-2013, 08:08 PM

Quote:

Originally Posted by Ryephile

Boost Threshold = The power in which a certain level of boost is achieved. This is usually best understood as the RPM in which the turbo "kicks in"

Turbo Lag = The time needed within the operational envelope of the turbo [between the compressors' choke and surge lines] for the turbo to create noteworthy airflow beyond natural aspiration versus the throttle opening.

For what it's worth, attempting to describe turbo lag below the boost threshold is a misapplication of terminology.

^This.

Your boost threshold is basically the RPM where the motor flows enough volume to allow the turbo to reach target boost.

Turbo lag is how long it takes the turbo to build boost if it is past the boost threshold.

Simon99 · 06-11-2014, 01:00 AM

Instead of making a thread, I'll necro one.

Which turbo kit on the forum uses the biggest turbo and therefore has the highest threshold/turbo lag ?

And which one is the opposite ?

Sent from my SGH-I337M using Tapatalk

SmsAlSuwaidi · 06-11-2014, 02:57 AM

Quote:

Originally Posted by Simon99

Instead of making a thread, I'll necro one.

Which turbo kit on the forum uses the biggest turbo and therefore has the highest threshold/turbo lag ?

And which one is the opposite ?

Sent from my SGH-I337M using Tapatalk

@FullBlown 6466 drag build

Avo and people on 50trim turbos

Simon99 · 06-11-2014, 03:21 AM

Quote:

Originally Posted by SmsAlSuwaidi

@FullBlown 6466 drag build

Avo and people on 50trim turbos

thanks ! it might sound weird but I love lag, coming from a big turbo ms3, the kick you get out of it is amazing. im probably not looking for a drag build, but something that makes full psi around 4.5-5 is something im looking for !

SmsAlSuwaidi · 06-11-2014, 03:22 AM

Quote:

Originally Posted by Simon99

thanks ! it might sound weird but I love lag, coming from a big turbo ms3, the kick you get out of it is amazing. im probably not looking for a drag build, but something that makes full psi around 4.5-5 is something im looking for !

I make 18 by 4450 or so

Sent from my IBrick

Simon99 · 06-11-2014, 03:23 AM

Quote:

Originally Posted by SmsAlSuwaidi

I make 18 by 4450 or so

Sent from my IBrick

build thread link ? :o what kind of internals do you have

xwd · 06-11-2014, 10:49 AM

Most kits using a GT3076 will spool around there and probably give you what you are looking for. Most of the popular kits out there can accommodate a GT30. PTuning uses one as their base turbo.

Alternatively if you are using a EBCS and Ecutek to control boost, you can artificially make the car behave that way even with a small turbo if you really want.

King Tut · 06-11-2014, 11:06 AM

The ultimate power goal is really what should be determining your turbo selection. What are your goals for the car?

Simon99 · 06-11-2014, 01:18 PM

Quote:

Originally Posted by King Tut

The ultimate power goal is really what should be determining your turbo selection. What are your goals for the car?

don't call me dumb, but the highest possible on stock internal (in the long run)

Reaper · 06-11-2014, 01:29 PM

Gtx2867r will make the most wtq under 460whp compared to larger turbos. Larger turbos like the gtx30 and 35 will make more whp and eventually more wtq but you end up over 530whp before it makes the same wtq as the gtx28 did at 450whp. I wasnt comfortable at 530whp but I wanted the most wtq I could get on stock internals so I went with the gtx28.

Sent from my SAMSUNG-SGH-I747 using Tapatalk

King Tut · 06-11-2014, 01:59 PM

Quote:

Originally Posted by Simon99

don't call me dumb, but the highest possible on stock internal (in the long run)

Unknown really. I would say keep it under 400 whp on E85 in the long run and just over 300 whp on 93.

11-07-2012, 05:37 PM	#15
Ryephile Hot Dog Join Date: Apr 2011 Drives: quicker than arghx7 Location: Metro Detroit Posts: 1,316 Thanks: 103 Thanked 173 Times in 83 Posts Mentioned: 6 Post(s) Tagged: 0 Thread(s)	Boost Threshold = The power in which a certain level of boost is achieved. This is usually best understood as the RPM in which the turbo "kicks in" Turbo Lag = The time needed within the operational envelope of the turbo [between the compressors' choke and surge lines] for the turbo to create noteworthy airflow beyond natural aspiration versus the throttle opening. For what it's worth, attempting to describe turbo lag below the boost threshold is a misapplication of terminology. Example: A GT35R is bolted onto your friends Evo IX. It has a dyno-pull WOT boost threshold of 5k RPM [just go with it]. If he floors it at 3k RPM, the car is turtle slow and essentially naturally aspirated. This is not turbo lag, and the turbo is operating below it's boost threshold. He keeps his foot to the floor, and once the engine reaches 5k RPM, the turbo reaches boost and the car rockets away into the sunset. Now let's say he's downshifted and is cruising along steady at 6k RPM, then floors the throttle. The turbo takes time to spool, this is the turbo lag. The engine as a system also has to create a certain amount of power to spool the turbo. Once that certain level happens, the car rockets off into the horizon. You've now hit the boost threshold, even though it happened at 6k. If my example is confusing, it's also nicely explained on Wikipedia. __________________ "Wisdom is a not a function of age, but a function of experience." Just Say No to unqualified aftermarket products.

06-11-2014, 11:06 AM	#25
King Tut NASA SpecE30 Racer Join Date: May 2012 Drives: 2006 Honda S2000 Location: Gulf Breeze, FL Posts: 7,279 Thanks: 607 Thanked 5,759 Times in 3,055 Posts Mentioned: 274 Post(s) Tagged: 10 Thread(s)	The ultimate power goal is really what should be determining your turbo selection. What are your goals for the car? __________________ - King Tut Street/Track Car: 2006 Honda S2000 TT3 \|\| Race Car: 1987 BMW 325is SpecE30 \|\| Tow Vehicle: 2014 RAM 1500 EcoDiesel Sold Cars: 2012 BMW M3 \|\| 2013 Subaru BRZ \|\| 2012 Porsche Cayman R \|\| 2009 Chevrolet Z06 \|\| 2009 BMW M3 \|\| 2004 BMW M3 \|\| 2004 Nissan 350Z

06-11-2014, 01:29 PM	#27
Reaper in orbe terrum non visi Join Date: Jan 2014 Drives: violent Location: Mountains Posts: 1,747 Thanks: 279 Thanked 762 Times in 446 Posts Mentioned: 62 Post(s) Tagged: 1 Thread(s)	Gtx2867r will make the most wtq under 460whp compared to larger turbos. Larger turbos like the gtx30 and 35 will make more whp and eventually more wtq but you end up over 530whp before it makes the same wtq as the gtx28 did at 450whp. I wasnt comfortable at 530whp but I wanted the most wtq I could get on stock internals so I went with the gtx28. Sent from my SAMSUNG-SGH-I747 using Tapatalk __________________ I have E85 where there isn't E85, that's my secret. http://www.ft86club.com/forums/showt...t=reaper+build

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